This invention concerns a method and an apparatus for classifying and recovering the main components of used batteries. More specifically, it concerns a method and an apparatus by which the batteries are conveyed on a conveyor while an alternating magnetic field is applied to each. A detection means detects what sort of induced magnetic field has resulted from the eddy current induced in the battery and in this way determines what sort of battery it is. The batteries being conveyed on the conveyor are brought to within a fixed distance of the detection means, and their travel path is constrained so as to maintain highly accurate detection.
In order to prevent environmental pollution, make the fullest possible use of natural resources and aid recycling, it is desirable to classify used batteries according to their main components.
Devices have therefore been developed which can be used to classify used batteries without destroying them. Such apparatus apply an alternating magnetic field to a used battery to generate an eddy current. By measuring the magnetic field induced by this eddy current, one can classify the battery according to its main components.
However, the exterior of a battery is usually covered with an ornamental steel jacket which has a tendency to influence the magnetic characteristics.
In Japanese Patent Publication 6-215802, a design was proposed in which an alternating magnetic field was applied to the used battery and a very large magnetostatic field (a quasi-magnetostatic field) was also applied. The magnetostatic field would magnetically saturate the steel jacket.
The battery separator proposed in Japanese Patent Publication 6-215802 is characterized by the following features. It has at least one excitation coil (20), which is connected to three excitation means (21, 22 and 23) and which generates an alternating magnetic field; a positioning means to position the battery or storage battery (10) in the alternating magnetic field; three detection means (30, 31 and 32), which measure the induction while the battery or storage battery (10) is in the alternating magnetic field; and four means (41, 42, 24 and 34) to induce a quasi-magnetostatic field in the battery whose properties are being measured via the induction. The quasi-magnetostatic field will virtually saturate at least a part of the ferromagnetic portion of the battery or storage battery (10).
The numbers given above are those used in the drawings appended to Patent Publication 6-215802.
As is explained in the Patent Publication 6-215802, when the jacket of the battery is magnetically saturated, the magnetic characteristics of the used battery are no longer influenced by the jacket, but are now determined by the main components constituting the battery within the Jacket. Thus by measuring the field created by the eddy current induced by the alternating field, one can determine what the main components of the battery are.
However, in the prior art technique, when the steel jacket of the used battery is magnetically saturated, an attraction force is generated between the jacket and the coil. Thus this method is not suitable for continuous sorting of batteries.
If the batteries are positioned one by one inside the coil and a magnetic field is applied to them, the method described above can be used successfully to sort the batteries by composition. However, if a very large magnetostatic field is applied while a large number of batteries are being continuously fed or dropped into the coil, the batteries will be attracted to the coil when the field is applied, and the feed will be interrupted. This makes continuous sorting problematical.
When an alternating magnetic field is applied to the used batteries so that the induced magnetic field which is generated can be measured, the batteries, which are being conveyed on a belt, must be prevented from shifting up, down, left or right on the belt. When they are in position to be detected by the detection means, the distance between the battery and the detection means must remain fixed; and the batteries must be transported smoothly, without getting hung up.
However, because the prior art technique makes use of a saturation field, the field strength is extremely large. In practical terms, this means that it is difficult to achieve a smooth movement of the batteries on the belt.
In view of the shortcomings of the prior art, the object of this invention is to enable continuous bulk sorting of batteries, to assure a smooth feed, and to improve the accuracy with which the induced magnetic field generated in the battery is detected.
To address the aforementioned shortcomings in the prior art, the present invention is designed as follows. The method of sorting batteries according to the invention entails inducing in a battery being continuously conveyed a weak magnetic field and an alternating magnetic field containing numerous frequency components. The induced magnetic field created by the eddy current induced in the battery is then detected to determine what sort of battery it is. The strength of the induced magnetic field and the phase-shift are detected with respect to the alternating field. Based on the relationship between the classification/the size of the battery with respect to the strength/the phase-shift of the induced magnetic field which were previously obtained, the battery is then sorted according to type and size.
A further refinement of the method of sorting batteries according to the invention is characterized by the fact that the strength of the magnetostatic field is between 0.01 T (Teslas) and 0.3 T.
Another embodiment of the method of sorting batteries according to the invention entails inducing in a battery being continuously conveyed an alternating magnetic field containing numerous frequency components. The induced magnetic field created by the eddy current induced in the battery is then detected to determine what sort of battery it is. The strength of the induced magnetic field and the phase-shift are detected with respect to the alternating field. Based on the relationship between the classification/the size of the battery with respect to the strength/the phase-shift of the induced magnetic field which were previously obtained, the battery is then sorted according to type and size.
A further development of the foregoing method of sorting batteries is further characterized by the fact that the relationship between the type and size of the battery, and the strength and phase of its induced magnetic field has a tolerance range for every frequency component of the alternating field. From the set of tolerance ranges, the type and size of the battery can be determined.
Another refinement of the method of sorting batteries according to the invention is further distinguished by the fact that the strength of the magnetostatic field should be set at a level such that the feed of the batteries is not hindered.
With this invention, an eddy current is generated in batteries which differ in their main constituents. The induced magnetic field resulting from this eddy current causes characteristic changes depending on the materials which constitute the battery. By detecting these changes, the batteries can be sorted by their main ingredients.
In particular, if a weak magnetostatic field is superposed on an alternating field, the differences between the variations in eddy current which are observed with different sorts of batteries will be enhanced. Reducing or not applying the magnetostatic field allows the batteries to be conveyed at high speeds.
Using signals of multiple frequencies allows batteries to be sorted by composition with greater accuracy. Combining a number of sorting apparatuses allows batteries to be sorted by composition even though they may be of different sizes or shapes.
In a preferred embodiment of the invention, the strength of the magnetostatic field is between 0.01 T (Teslas) and 0.3 T, or {fraction (1/10)} the field strength in the prior art apparatus. Because the field strength was so large in the prior art apparatus, stability could not be maintained in the battery feed. With the weaker field, the accuracy with which the induced magnetic field can be detected does not suffer, the frictional resistance of the batteries as they are transported on the conveyor is reduced, and the batteries can be moved smoothly.
The invention also includes apparatus for implementing the method of sorting batteries according to the invention. One embodiment of apparatus for sorting batteries according to the invention rotates a disk which is oriented obliquely and a second horizontal disk surrounding the first on an axis which intersects both disks. The outer disk is rotated faster than the inner, and the batteries are inserted at their common center. As the disks rotate, the batteries are arranged at fixed intervals, and this row of batteries is conducted via conveyor belt past a device which generates a weak magnetic field, one which generates an alternating magnetic field, and one which detects changes in the induced magnetic field. This device detects changes in the strength and phase of the induced magnetic field which are due to the composition of the battery for frequency components in at least two ranges. A signal processing device applies xe2x80x9cANDxe2x80x9d and xe2x80x9cORxe2x80x9d logical operations to the data which are detected, and outputs them as a signal corresponding to what sort of battery each is. This output is used to send each sort of battery to a specific location.
Another embodiment of apparatus for sorting batteries according to the invention is characterized by the fact that it lacks the device for generating a weak magnetic field which is present in the previously described embodiment.
Another embodiment of apparatus for sorting batteries according to the invention is characterized by the fact that the conveyor belt is tilted along the axis of its width, and a device is used which lines up and conveys the batteries so as to stabilize the position of each battery as it passes the field generators.
A further embodiment of apparatus for sorting batteries according to the invention is characterized by the fact that the coil for inducing an alternating current, which is used as the device to generate an alternating magnetic field, and the detector coil, which is used as the device to detect changes in the induced magnetic field, are both local type coils. One of these coils is large and the other small. Both are placed on the same shaft. This arrangement gives the device the capacity to detect the composition of both large and small batteries.
With the apparatus according to the invention,
(1) A rotating conveyor device feeds the batteries at fixed intervals. This arrangement prevents the detected signal of the battery from being disturbed by the noise signal generated by the next battery in line, thus improving the sorting capacity.
(2) The conveyor belt is tilted. The batteries being conveyed are brought past a fixed position with respect to the width of the belt. This minimizes variations of the detection signal, thus improving the sorting capacity.
(3) The local excitation coils are placed either above or below the conveyor belt. This improves the sensitivity of detection with respect to flat batteries.
(4) The size and shape of the local coils can be selected to correspond to the type and shape of the batteries being sorted. This allows a larger amplitude detection signal to be used, thus improving the sorting capacity.
(5) The coil used to detect changes in the induced magnetic field is placed orthogonal to the direction of the magnetostatic field. This enhances the effect of the magnetostatic field operating on the battery, thus improving the sorting capacity.
The invention also concerns a method for constraining the transport path of the batteries in order to bring each battery to within a fixed distance of the detection means.
In one embodiment of the method for sorting batteries according to the invention, an alternating magnetic field containing a number of frequency components is applied to a battery being continuously conveyed on a conveyor belt. The battery is then sorted by detecting the induced magnetic field resulting from the eddy current induced in it. This method is characterized by the following. A magnet is placed near the position in which the induced magnetic field is detected. The attraction of the magnet causes the battery on the conveyor belt to be drawn into the detection region, and the induced magnetic field is detected.
In a further development of the method of sorting batteries according to the invention the method is further characterized by the fact that the induced magnetic field is detected from beside the conveyor belt. The magnet is placed near the detection region so that the battery will be drawn into that position.
In another further development of the method of sorting batteries according to the invention the method is further characterized by the fact that the magnet is a U-shaped magnet. The detection region and the path of transport of the battery are located between the poles of this magnet.
Another refinement of the method of sorting batteries according to the invention is further distinguished by the fact that the induced magnetic field is detected from beside the conveyor belt. The magnet is placed in the detection region below the conveyor belt.
In the embodiments of the invention described above, the battery is drawn toward the detection means by the attractive force of the magnet so that it cannot slip forward or back, left or right in the detection region. The distance between the battery and the detection means is kept fixed so that the transport of the battery is stabilized. This arrangement facilitates achievement of high accuracy of detection.
In one preferred embodiment of the invention, a U-shaped magnet is used. This makes the magnetic field difficult to interrupt and contributes to the achievement of a strong field, resulting in more closely constrained transport of the battery.
In another preferred embodiment of the invention, the magnet is placed under the conveyor belt. The battery is pulled downward against the surface of the belt. The coefficient of friction between the battery and the belt surface is increased, and stable transport of the battery is achieved.
The invention further relates to apparatus for mechanically stabilizing the transport of the battery. One embodiment of the battery sorting apparatus according to the invention has a means for applying an alternating magnetic field containing a number of frequency components to the battery being conveyed continuously on the conveyor belt and a means for detecting the induced magnetic field created by the eddy current induced in the battery. Near the detection means are a belt to stabilize the position of the battery, which is driven by a drive means either to rotate or to move back and forth, and an elevation means to raise and lower the belt. A position-stabilizing mechanism uses the belt to force the battery on the conveyor belt toward the detection means.
Another embodiment of the apparatus for sorting batteries according to the invention has a means for applying an alternating magnetic field containing a number of frequency components to the battery being conveyed continuously on the conveyor belt and a means for detecting the induced magnetic field created by the eddy current induced in the battery. This embodiment is distinguished by the fact that the conveyor belt has ridges at fixed intervals along the length of its surface. In the vicinity of the detection means, the battery can engage in one of the depressions formed between each two ridges.
A further embodiment of the apparatus for sorting batteries according to the invention has a means for applying an alternating magnetic field containing a number of frequency components to the battery being conveyed continuously on the conveyor belt and a means for detecting the induced magnetic field created by the eddy current induced in the battery. This embodiment is distinguished by the fact that the conveyor belt has an undulating surface.
Yet another embodiment of the apparatus for sorting batteries according to the invention also has a means for applying an alternating magnetic field containing a number of frequency components to the battery being conveyed continuously on the conveyor belt and a means for detecting the induced magnetic field created by the eddy current induced in the battery. This embodiment is distinguished by the fact that it has a guide panel near the detection means, which is above the surface of the conveyor belt, to guide the battery on the belt toward the detection means.
In the aforedescribed embodiments of the apparatus according to the invention, a mechanical means is used while the battery is being conveyed to draw the battery toward the detection means. This arrangement allows the transport path of the battery to be constrained without any noise appearing in the signal from the detection means, a problem which occurs when a magnet is used.
A still further embodiment of the apparatus for sorting batteries according to the invention likewise has a means for applying an alternating magnetic field containing a number of frequency components to the battery being conveyed continuously on the conveyor belt and a means for detecting the induced magnetic field created by the eddy current induced in the battery. This embodiment is distinguished by the fact that it has a magnetic belt adjacent to the detection means, on which the battery is conveyed. With this embodiment of the invention, the battery sits on a magnetic belt to which it adheres magnetically. This prevents incidental motion from occurring while the induced magnetic field is being detected, thus assuring stable transport of the battery and maintaining a high accuracy of detection.
Another embodiment of apparatus for sorting batteries according to the invention has a means for applying an alternating magnetic field containing a number of frequency components to the battery being conveyed continuously on the conveyor belt and a means for detecting the induced magnetic field created by the eddy current induced in the battery. At the very start of the conveyor belt, there is a device to control the spacing of the batteries so as to assure an equal interval between the batteries being transported on the belt. This arrangement reduces the likelihood that an adjacent battery will affect the process when a given battery""s induced magnetic field is detected and so assures a high accuracy of detection.